This invention relates to a variable capacity vane compressor, and more particularly to improvements in bearing means for a capacity control element used in a variable capacity vane compressor.
A conventional variable capacity vane compressor for use in automotive air conditioners, as proposed by Japanese Provisional Patent Publication (Kokai) No. 63-205493comprises, as shown in FIG. 1, a cylinder formed by a pair of side blocks 3, 4, and a cam ring 1 having opposite ends closed by the associated side blocks 3, 4, a rotor 2 rotatably received in the cylinder, and a drive shaft 7 on which the rotor is rigidly fitted. The side blocks 3, 4 have respective through holes 40, 41 through which the drive shaft 7 extends. Radial bearings 8, 9 are force-fitted in the respective through holes 40, 41 for supporting the drive shaft 7. The rear side block 4 has an annular recess 23 formed in a rotor side face 4a thereof. A capacity control element 24 in the form of an annulus is rotatably fitted in the annular recess 23 for controlling timing of the start of compression of a refrigerant gas. The control element 24 is supported by a thrust bearing 43 fitted in an annular recess 42 formed in an inner peripheral surface of the through hole 41 of the rear side block 4. The thrust bearing 43, which is sandwiched between an end wall 42a of the annular recess 42 facing toward the rotor 2 and an opposed side face 24a of the control element 24, supports the control element 24 only in the axial direction.
The control element is directly fitted on the drive shaft 7, with its central through hole 24b penetrated by the shaft 7.
The control element 24 is rotatable between the maximum capacity position and the minimum capacity position to vary the capacity or delivery quantity of the compressor between the maximum value and the minimum value.
A torsional spring 38 has one end thereof engaged by a rear head 6 and the other end by the control element 24 to bias the latter in the capacity-decreasing direction.
However, the control element 24 is also biased in the radial direction so that the central through hole 24b of the control element 24 is not coaxial with the drive shaft 7. That is, the inner peripheral surface of the central through hole 24b is constantly in line contact with the outer peripheral surface of the drive shaft as shown in FIG. 2 such that the control element 24 is guided by the drive shaft 7. Consequently, when the compressor 7 rotates at a high speed or the compressor is in a high load condition, there may occur galling between the control element 24 and the drive shaft 7, which prevents smooth rotation of the control element, degrading the controllability of the compressor, and causes the drive shaft 7 and the control element 24 to be rapidly worn, degrading the reliability.